1. Field of the Invention
The present invention relates to the transporting of individual documents and particularly to the controlled uninterrupted movement of indicia bearing sheets of paper, withdrawn from a stack of sheets, past the image capture device of an optical character recognition apparatus. More specifically, this invention is directed to apparatus for continuously transporting documents in serial fashion past a work station and especially to a paper conveyor of modular design for use in conjunction with document scanning apparatus such as in OCR and other imaging applications. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
Many business machines, machines which copy documents and computer controlled printers for example, include a paper transport. The paper transport has acquired the reputation of being the "weak link" in such machines, i.e., equipment malfunctions or "jams" most often occur in the extraction of a page from a stack or during the transport of an extracted page through the machine. In addition to being the most prevalent source of malfunction, existing paper transports often impose the limitation on the upper rate of document throughput.
It is a truism that the more sophisticated the application, the more troublesome will be any malfunction associated with a document transport. While not limited thereto in its utility, the present invention is particularly well suited for perhaps the most demanding application which requires that single sheets of information bearing paper be moved past a work station, namely applications which include document imaging such as optical character recognition. In order to justify the cost of the optical character recognition hardware and software, or other imaging application associated computer hardware and software, the user must be assured of reliable operation and a high document throughput rate. Thus, the paper transport which is coupled to the application dictated hardware must be characterized by a high degree of reliability and particularly minimization of "jams". Also, where complex de-shewing electronics is not employed, the transport must also be characterized by the ability to ensure that the documents being "read" are properly oriented relative to the "camera" and securely held in the established orientation during movement. Additionally, since the imaging of a document will typically be performed with the document moving at a slower velocity than the maximum reliably obtainable transport speed, a paper transport for an OCR application will optimally have the capability of moving a document at plural speeds, i.e., a "reading" velocity and a faster downstream velocity.
Previously available paper transports have failed to meet one or more of the above-listed requirements, i.e., reliability, de-skewing, secure transport and the ability to change transport speed. Additional requirements of a high performance paper transport system include ease of installation and maintenance, and particularly the ability to quickly and easily clear jams. A further desirable attribute of a high performance transport would be a configuration which permitted the user a degree of flexibility in locating work stations, such as imaging devices, microfilm cameras and printers, and also flexibility in the choice of work station device. Also, the optimal transport for an OCR application would ensure that the documents being processed are treated gently and move constantly through the work station areas, i.e., there is no stop and start motion which might produce misalignment. The optimal transport would also provide for constant velocity document motion in the work station area(s). As another requirement, since most OCR applications require that documents be serially processed in the order in which stacked, the transport system should preferrably include document justification including the capability of detecting an inadvertent multiple page feed or the absence of a document.